This invention relates to the monitoring of electromagnetic power for safety purposes.
In the past, high power electromagnetic radiators could be sited well away from populated areas. For example, when long-wave transatlantic radio communications were begun, the site selected for the very large transmitting antennas was on Long Island, then a sparsely populated region. High power electromagnetic radiators must be designed and manufactured, and the design and manufacturing process involves relatively large numbers of skilled personnel, ordinarily found only in urban and suburban regions. Thus, high power electromagnetic radiators may sometimes be found in urban or suburban locations when design, testing or manufacture is involved. Also, high power electromagnetic radiators may occasionally be sited in densely populated areas, such as major airports.
It has long been known that high power electromagnetic radiators could be harmful to humans and animals. The harmful heating effects of even low-power radars, as well as the potential of certain body structures, such as eye sockets, for exacerbating heating effects, were well known in the 50s. Also, the cold-war-era Ballistic Missile Early Warning System (BMEWS) included radar of such high power that food subject to the transmissions could literally be cooked, and it was well understood that animal tissues similarly placed could be severely harmed.
While no study has shown that electromagnetic radiation is harmful to people at power levels below those which cause heating effects, many people are made uncomfortable by the thought of being subjected to radio-frequency electromagnetic radiation, even from low-power sources such as cell phones. In the past, notwithstanding the cost, surveys of the region surrounding electromagnetic radiation sites have been made using portable sensors, and plots of the radiation intensity made from the recorded results. These plots could then used as a basis for determining the risk to the local population. The operators of a facility which operates electromagnetic radiating systems such as radars, radio or television transmitters may deem it advisable to keep the surrounding community advised of the nature of any radiations, and to make other efforts to allay the fears of the population. Improved methods for measuring and controlling electromagnetic radiation from a fixed site are desirable.
According to an aspect of the invention, an integrated electromagnetic radiation monitoring system is for monitoring a set of controllable radiation sources (which may be only one source) which, when operating, radiate electromagnetic energy having wavelengths greater than that of infrared, where the radiation sources are capable of being shut down by radiation inhibit signals. The monitoring system includes a plurality of sensors spaced about the set of radiation sources, for sensing at least one of peak and average electromagnetic power within at least some of the wavelengths, for producing digitized signals representing the peak or average power. Additionally, the monitoring system includes a control arrangement coupled to the set of radiation sources and to the plurality of sensors, for comparing the digitized signals with a given threshold level, and for, in response to the digitized signals exceeding the threshold, generating the inhibit signals, whereby the radiation sources are shut down when the sensed electromagnetic power exceeds the threshold.
In a particular embodiment of the invention, the control arrangement further activates an alarm signal concurrently with the generation of the inhibit signals. The alarm signal may ultimately result in sounding of an aural or visual alarm.
In a particularly advantageous embodiment of the monitoring system, the control arrangement further compares the digitized signals with a second threshold level. The second threshold level represents less sensed power than that represented by the given threshold level, and generates a warning signal when the second threshold level is crossed.